High breakdown voltage ZnMgO/In-Ga-Zn-O heterostructure transistors

ZnO-based semiconductors with the wide-band gap have attracted great interest for electronic and optical applications [1]. Among them, an amorphous In-Ga-Zn-O (a-IGZO) has been intensively studied [2,3]. The thin-film transistors using of a-IGZO as an active n-channel layer exhibit good performances such as the high field-effect mobility [μFE ∼ 10 cm² (Vs)⁻¹], Ion/Ioff ratio of ∼10⁸, and excellent process stability, even when the channel layer was deposited at room temperature (RT). The band gap of a-IGZO was estimated to Eg = 3.1–3.4 eV from several spectroscopic techniques [4], which is a promising candidate for high voltage applications such as switching devices for power supplies. Moreover, a-IGZO films have the high uniformity in large area owing to the amorphous character, which results in low-cost fabrication.